Add alloy wrapper for groupbyattrs processor

[MargaretKrutikova]

Request

alloy is missing a wrapper for groupbyattrsprocessor from opentelemetry-collector-contrib.

Use case

We are using alloy to scrape metrics from kube-state-metrics and apply transformations to make it OTEL compatible. kube-state-metrics sets labels of the scraped pod which we then want to pipe through alloy processors to change the names e.g., however, from what we have noticed, if we are using the available processors like otelcol.processor.transform the attribute values get really screwed and it looks like a randomly selected value gets applied to the attribute value for the metrics of all the pods in the scraped set of metrics.

We suspect that the only way to achieve what we need is to use is groupbyattrsprocessor from opentelemetry-collector-contrib. What it be possible to add a wrapper for this processor in alloy?